De novo organogenesis and plant regeneration in <Emphasis Type="Italic">Pongamia pinnata</Emphasis>, oil producing tree legume

Role of Thidiazuron (TDZ) in inducing adventitious organogenesis in Pongamia was studied. TDZ at different concentrations (0, 0.45, 2.27, 4.54, 6.71, 9.08, 11.35, 13.12 and 22.71 μM) were used for induction of caulogenic bud formation in deembryonated cotyledon explants. Each cotyledon was cut into three segments and identified as proximal, middle and distal. Duration of TDZ exposure, influence of the segment and orientation of the explant were studied. TDZ at 11.35 μM concentration was optimum for the induction of shoots and rapid elongation. Shoots induced at higher concentration elongated after several passages in growth regulator free medium, thereby extending the period of differentiation. Exposure of the explant for 20 days yielded more number of buds than 10 days. Proximal segment of the cotyledon was more responsive. Contact of abaxial surface in the medium was more effective and generated more buds than the adaxial side. Buds differentiated and elongated on transfer to MS basal medium for 8–12 passages of 15 days each. Rooting and elongation of shoots was achieved in charcoal supplemented half-strength MS medium. Rooted plantlets survived on transfer to sand soil mixture. The plants were hardened and transferred to green house. This is the first report on in vitro regeneration of Pongamia pinnata via adventitious organogenesis using TDZ. This protocol may find application in studies in genetic transformation, isolation of somaclonal variants and in induction of mutants. It also provides a system to study the inhibitory role of TDZ on shoot differentiation.     

Ca2(+)-dependent glucose transport in chicken intestine

Transport of glucose was measured in the intestine of white leghorn layers in vivo using ligated upper small intestinal segment in the presence of Ca2+ and other ions either singly or in combination. Transport of glucose across the intestine was very significantly increased with Ca2+ than Na+, K+ and Po4(3-) individually, but when Ca2+ was combined with Na+, K+ and PO4(3-), the glucose absorption increased significantly over that achieved by Na+ ions alone. These data revealed that Ca2+ ions might be exerting the major influence on glucose transport processes of the chicken intestine.     

Effect of mode of operation of bioreactors on the biosynthesis of penicillin amidase in Escherichia coli

Different operational mode of bioreactors influence the biosynthesis of the enzyme and related products as well as the growth of industrial microorganisms. This communication deals with the effect of mode of operation of various bioreactors with different geometric configurations, viz., batch (includes commercially available batch stirred tank, and custom-designed cylindrical and tapered reactors), batch-fed, continuous flow stirred tank reactors on the biosynthesis of penicillin amidase in Escherichia coli. Experimental findings show that the biosynthesis of penicillin amidase in E. coli show a little variation among batch reactor modes and significant variation on the continuous mode of operation. Further analysis show that the different reactor modes also influence periplasmic localization of the enzyme in the cell.     

Parameters optimization of chitin hydrolysis by Trichoderma harzianum chitinase under assay conditions

A kinetic analysis and optimization of reaction conditions for the enzymatic hydrolysis of chitin using chitinase produced by Trichoderma harzianum NCIM 1185 was carried out. Swollen chitin was used as the substrate for chitinase. The central composite design was followed for this optimization. The required volume ratio of the major reactants for maximum hydrolysis was determined. The pH and temperature optima were found to be 4.75 and 47 °C respectively. K _m and V _max for this enzyme were 4.643 kg/m³ and 0.1542 U respectively.     

Identification of a new group-specific determinant on hepatitis B surface antigen with a synthetic peptide.

In a recent study we demonstrated that a synthetic peptide representing residues 124-147 of the major protein of hepatitis B surface Ag (HBsAg) undergoes spontaneous oligomerization to reconstruct one or more conformational group-specific determinants on HBsAg. The present study was undertaken to identify and characterize the HBsAg-related antigenic determinants on this oligomeric peptide (peptide OS[124-147]). A panel of nine analogs of this peptide was generated by either deleting, substituting, or chemical side chain modification of specific amino acid residues. With HBsAg subtype-specific antisera a single "a" epitope was identified as one that includes Met133 and Lys141. In addition a "d" epitope toward the amino-terminal end of the sequence was also observed. Perturbation of certain amino acid residues was found to enhance a antigenicity and subsequent experiments indicated that maximal expression of this a antigenicity is dependent in part on accessibility of the Lys141 side chain and in part on the primary sequence. With a total of 50 human anti-HBsAg serum samples obtained from individuals vaccinated against hepatitis B, it was demonstrated that these sera recognize the Met133-Lys141-dependent a epitope as the dominant, and in many cases the only, determinant on peptide OS[124-147]. Finally, on immunization, peptide OS[124-147] elicits an anti-HBsAg response that is predominantly anti-a though a lesser contribution from an anti-d response was also obtained.     

Morphological and molecular divergence of Indian hill trout,Barilius bendelisis (Hamilton, 1822) stocks from different Rivers in Indo‐Burma biodiversity hotspot: Does river altitude and Dam play a role?

The present study explains the intraspecific variation in Indian Hill trout (Barilius bendelisis) on the basis of image based truss network system and D‐loop region of mtDNA. A total of 210 samples were collected from three different rivers (Teesta, Kameng and Myntudu River) of North East India in Indo‐Burma Biodiversity Hotspot. By using the software applications (tpsDig version 2.1 and PAST), a total of 25 morphometric measurements were generated from 10 landmarks. The Analysis of Variance (ANOVA), Factor Analysis (FA) and Discriminate Function Analysis (DFA) showed, out of the total variations, factor 1 explained 46.74% while factor 2 and factor 3 explained 27.14% and 11.92%, respectively. Using these variables 83.33% of the cross‐validated specimens were classified into distinct groups. Analysis of Molecular Variance (AMOVA) and pairwise Fst value for D‐loop region of mtDNA also showed high to medium level of genetic variation among the stocks and within the stocks. We conclude that the observed discrete stocks might be the result of changing environmental conditions in different rivers of the hotspot as the rivers are present at different altitudinal labels. It is also believed that the variation might be due to the construction of barrages across the river which hinder the mixing among the stocks.     

Optimization of carbon and nitrogen sources in the medium and environmental factors for enhanced production of chitinase by Trichoderma harzianum

Statistical design was used to determine the optimal levels of medium components, the optimal initial pH of the enzyme production medium, the temperature of fermentation, age of the organism in the slant growth and the age of the inoculum for the production of chitinase in shake flask fermentations. The use of high concentrations of chitin and ammonium sulphate and exclusion of peptone and urea from the medium resulted in the production of higher level of the enzyme. The optimal concentrations of the medium components were 12.5 kg/m³ and 4.2 kg/m³ for the chitin and ammonium sulphate respectively. The effect of the addition of peptone and urea to the optimized medium was studied. The optimal values of initial pH and temperature were 5.6 and 28 °C respectively. The optimal age of the slant and the inoculum were found to be 105 h and 43 h respectively. The highest level of chitinase before optimization of the above variables was 0.054 U which was maximized to the level of 0.197 U.     

Newcastle disease virus V protein is associated with viral pathogenesis and functions as an alpha interferon antagonist

Newcastle disease virus (NDV) edits its P gene by inserting one or two G residues at the conserved editing site (UUUUUCCC, genome sense) and transcribes the P mRNA (unedited), the V mRNA (with a +1 frameshift), and the W mRNA (with a +2 frameshift). All three proteins are amino coterminal but vary at their carboxyl terminus in length and amino acid composition. Little is known about the role of the V and W proteins in NDV replication and pathogenesis. We have constructed and recovered two recombinant viruses in which the expression of the V or both the V and W proteins has been abolished. Compared to the parental virus, the mutant viruses showed impaired growth in cell cultures, except in Vero cells. However, transient expression of the carboxyl-terminal portion of the V protein enhanced the growth of the mutant viruses. In embryonated chicken eggs, the parental virus grew to high titers in embryos of different gestational ages, whereas the mutant viruses showed an age-dependent phenomenon, growing to lower titer in more-developed embryos. An interferon (IFN) sensitivity assay showed that the parental virus was more resistant to the antiviral effect of IFN than the mutant viruses. Moreover, infection with the parental virus resulted in STAT1 protein degradation, but not with the mutant viruses. These findings indicate that the V protein of NDV possesses the ability to inhibit alpha IFN and that the IFN inhibitory function lies in the carboxyl-terminal domain. Pathogenicity studies showed that the V protein of NDV significantly contributes to the virus virulence.     

Neutralizing a Surface Charge on the FMN Subdomain Increases the Activity of Neuronal Nitric-oxide Synthase by Enhancing the Oxygen Reactivity of the Enzyme Heme-Nitric Oxide Complex

Nitric-oxide synthases (NOSs) are calmodulin-dependent flavoheme enzymes that oxidize l-Arg to nitric oxide (NO) and l-citrulline. Their catalytic behaviors are complex and are determined by their rates of heme reduction (k_r), ferric heme-NO dissociation (k_d), and ferrous heme-NO oxidation (k_ox). We found that point mutation (E762N) of a conserved residue on the enzyme''s FMN subdomain caused the NO synthesis activity to double compared with wild type nNOS. However, in the absence of l-Arg, NADPH oxidation rates suggested that electron flux through the heme was slower in E762N nNOS, and this correlated with the mutant having a 60% slower k_r. During NO synthesis, little heme-NO complex accumulated in the mutant, compared with ∼50–70% of the wild-type nNOS accumulating as this complex. This suggested that the E762N nNOS is hyperactive because it minimizes buildup of an inactive ferrous heme-NO complex during NO synthesis. Indeed, we found that k_ox was 2 times faster in the E762N mutant than in wild-type nNOS. The mutational effect on k_ox was independent of calmodulin. Computer simulation and experimental measures both indicated that the slower k_r and faster k_ox of E762N nNOS combine to lower its apparent K_m,O2 for NO synthesis by at least 5-fold, which in turn increases its V/K_m value and enables it to be hyperactive in steady-state NO synthesis. Our work underscores how sensitive nNOS activity is to changes in the k_ox and reveals a novel means for the FMN module or protein-protein interactions to alter nNOS activity.Nitric oxide (NO)² is a biological mediator that is produced in animals by three NO synthase isozymes (NOS, EC 1.14.13.39): inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) (1, 2). The NOS are modular enzymes composed of an N-terminal oxygenase domain and a C-terminal flavoprotein domain, with a calmodulin (CaM)-binding site connecting the two domains (3). During NO synthesis, the flavoprotein domain transfers NADPH-derived electrons through its FAD and FMN cofactors to a heme located in the oxygenase domain. The FMN-to-heme electron transfer enables heme-dependent oxygen activation and a stepwise conversion of l-Arg to NO and citrulline (4, 5). Heme reduction also requires that CaM be bound to NOS and is rate-limiting for NO biosynthesis (6–9).NOS enzymes operate under the constraint of having their newly made NO bind to the ferric heme before it can exit the enzyme (10). How this intrinsic heme-NO binding event impacts NOS catalytic cycling is shown in Fig. 1 and has previously been discussed in detail (10–13). The l-Arg to NO biosynthetic reaction (Fe^III to Fe^IIINO in Fig. 1) is limited by the rate of ferric heme reduction (k_r), because all biosynthetic steps downstream are faster than k_r. However, once the ferric heme-NO complex forms at the end of each catalytic cycle, it can either dissociate to release NO into the medium (at a rate k_d as shown in Fig. 1) or become reduced by the flavoprotein domain (at a rate k′_r in Fig. 1; equal to k_r) to form the enzyme ferrous heme-NO species (Fe^IINO), which releases NO very slowly (11, 12). Consequently, two cycles compete during steady-state NO synthesis (Fig. 1); NO dissociation from the ferric heme (k_d) is part of a “productive cycle” that releases NO and is essential for NOS bioactivity, whereas reduction of the ferric heme-NO complex (k_r′) channels the enzyme into a “futile cycle” that actually represents a NO dioxygenase activity. The rate of futile cycling is also determined by the rate of O₂ reaction with the ferrous heme-NO complex (at a rate k_ox in Fig. 1), which regenerates the ferric enzyme. Surprisingly, NOS enzymes have evolved to have a broad range of k_r (varies 40×), k_ox (varies 15×), and k_d (varies 30×) values (Table S1) (12). This causes each NOS to distribute quite differently during steady-state NO synthesis and gives each NOS a unique catalytic profile (12).Open in a separate windowFIGURE 1.Global kinetic model for NOS catalysis. Ferric enzyme reduction (k_r) is rate-limiting for the biosynthetic reactions (central linear portion). k_cat1 and k_cat2 are the conversion rates of the enzyme Fe^IIO₂ species to products in the l-Arg and N^ω-hydroxy-l-arginine (NOHA) reactions, respectively. The ferric heme-NO product complex (Fe^IIINO) can either release NO (k_d) or become reduced (k′_r) to a ferrous heme-NO complex (Fe^IINO), which reacts with O₂ (k_ox) to regenerate ferric enzyme. Enzyme partitioning and NO release are determined by the relative rates of k_r, k_ox, and k_d. This figure is adapted from Ref. 12.The enzyme physical and electronic factors that may set and regulate each of the three kinetic parameters (k_r, k_ox, and k_d) in NOS enzymes remain to be fully described. At present, the composition of the NOS flavoprotein domain and CaM appear to be primarily responsible for determining the k_r (14–17), whereas the composition of the NOS oxygenase domain is presumed to determine the k_d and k_ox (18, 19). Indeed, our recent point mutagenesis study identified a patch of electronegative residues on the FMN subdomain that are required to maintain a normal k_r and NO synthesis activity in nNOS, suggesting that subdomain electrostatic interactions are important in the process (20). We found particularly large effects when the negative charge at Glu⁷⁶² was neutralized via mutation to Asn. Remarkably, the NO synthesis activity of E762N nNOS was double that of wild-type nNOS, despite the mutant displaying a slow k_r that was half of wild type. In the current report, we show that the E762N mutation has an additional, unsuspected effect on the k_ox kinetic parameter of nNOS. How this effect alters distribution of the nNOS enzyme during steady-state catalysis, impacts the apparent K_m,O2, and leads to hyperactive NO synthesis is described. Our finding that the nNOS flavoprotein domain can tune a key kinetic parameter that defines the rate of a heme-based reaction in the nNOS oxygenase domain is unusual and suggests a means by which protein-protein interactions could regulate the catalytic behavior of nNOS.     

Endoglucanase from the mixed culture of Trichoderma reesei and Aspergillus wentii

The level of α-mannanase in mixed fungal culture of Trichoderma reesei, D1-6, and Aspergillus wentii, Pt 2804, affects the extracellular activities of cellulase. The endoglucanase component of the cellulase system is a glycoprotein having mannose and other sugars and sugaramines in its glycan moiety. Its activity is inhibited by α-mannanase. The inactivation of endoglucanase by α-mannanase can be prevented by galactose.